Joining text objects and cube
The issue is, as @TARDIS Maker pointed out the sub surf modifier that you applied to the dice object. Its effects are being applied to the text. To rectify this you can add a mean crease to the text to prevent the sub surf from taking effect. Select the vertices that make up the text and use Shift-E then 1. This will make your text appear exactly as before (Unlike holding edges which will cause minor rounding) with the added benefit of not having to apply the modifier (Maintaining a non-destructive workflow).